We shall use the clinical analysis of heart-lung interactions as the vehicle for training post-doctoral candidates. This is an excellent and proven productive pathway for mentoring because it is based in clinically relevant cardiopulmonary physiology and requires the trainee to learn to use state-of-the-art imaging techniques with broad applications to the operating room, ICU, general hospital ward and out- patient clinic. Ventilation and ventilatory maneuvers have profound and often poorly understood hemodynamic effects especially in the setting of cardio-respiratory failure. Although numerous investigators have studied heart-lung interactions, an accurate clinical application has been lacking. Our goal is to develop and validate clinically relevant and easily applicable bedside tools for the rapid and unambiguous diagnosis of the etiology of hemodynamic insufficiency and the impact of ventilatory and adjunct cardiovascular therapies upon it. We use as our research environment, the echocardiographic clinic and the cardiac surgery suite. To accomplish these goals we are testing three hypothesis: 1) Ventilation-induced changes in LV preload and afterload are non-linear between forceful and relaxed spontaneous and positive- pressure inspiration. 2) Low levels of positive end-expiratory pressure improve LV performance by minimizing ventricular interdependence and LV ejection asynchrony by increasing ITP. 3) LV contractile reserve and preload responsiveness (often opposite ends of the cardiac function spectrum) and arterial tone can be readily identified by analysis of the arterial pulse pressure responses to spontaneous and positive-pressure ventilation. We shall use state-of-the-art echocardiographic imaging techniques (acoustic quantification and tissue Doppler imaging) for complex analysis of LV performance and simple aortic-pulsed Doppler and arterial pressure waveform analysis to assess preload-responsiveness, contractile reserve and arterial tone to derive clinically useful information.